The conventional belt tightening device has been proposed as disclosed in, for example, the Japanese utility Model Laid-Open Gazette No. Hei 2-150166, which is proposed by the applicant of the present invention and so constructed that, as shown in attached FIG. 16, a windup shaft B provided at one side of a main body A is provided with a belt insertion slit C, a free end of an adjusting belt D having at one end thereof a hook is inserted into the slit of the windup shaft B so as to be windable and adjustable in its belt length, a fixed belt E having a hook fixed at one end thereof and at its other end to the other side of the main body A through a fixed shaft R. An operating lever F is swingably supported to the windup shaft B, and between the operating lever F and the windup shaft B is provided with a transmission mechanism H having a mechanical brake G for transmitting the power caused by the swinging motion of operating lever F to the windup shaft B.
In addition, the mechanical brake G comprises a driven disc J integrally provided at the windup shaft B, a driving member M having a gear L screwable with a threaded shaft K, a braking ratchet wheel N interposed between the driving member M and the driven disc J, and an anti-reverse-rotation pawl P swingably supported to the main body A a pivotal shaft S and engageable or disengageable with or from the ratchet wheel N, the transmission mechanism H comprising the mechanical brake G and a transmitting pawl Q supported to the lever F and engageable or disengageable with or from the gear portion L. In addition, in FIG. 16, reference letter T designates a collar.
Accordingly, the operating lever F is moved in a swinging motion, so that the driving member M is normally rotated through a feed pawl at the transmitting pawl Q and screws forwardly through the rotation, the driving member M, driving ratchet wheel N and driven disc J, are integrated, the power transmitted to the driving member M is transmitted to the windup shaft B to be rotatably driven, the adjusting belt D inserted into the windup shaft B is wound up, and the adjusting belt D and fixed belt E are stretched, thereby belt-tightening cargo within the belt.
In the case where the cargoes are belt-tightened as above-mentioned, the hooks at the fixed belt E and adjusting belt D are held by retaining member or eyes at the load-carrying platform of, for example, a truck, and the free end of the adjusting belt D inserted into the slit C of windup shaft B is pulled by hand to keep the fixed belt E and adjusting belt D in a predetermined stretched state, thereby swinging the operating lever F. The adjusting belt D is wound up onto the windup shaft B by rotation thereof caused by the swinging motion of operating lever F, whereby the belts D and E are stretched to tighten the cargoes. In order to release the cargo tightening, a return pawl of the transmitting pawl Q is engaged with the gear portion L at the driving member M and the lever F is swung. The swinging motion of the lever F reversely rotates the driving member M, so that the driving member M screws backwardly in the direction of moving away from the driven disc J, whereby the driving member M, braking ratchet wheel N and driven disc J are released from integration thereof. Hence, the windup shaft B can reversely rotate only by an amount of backward screwing of the driving member M and the adjusting belt D wound up to the windup shaft B is rewound to enable the belts D and E to be loosened.
As the above-mentioned, since the adjusting side belt D is inserted into the slit C provided at the windup shaft B and overlapped with the free end of the adjusting belt D inserted into the slit C so as to be wound up onto the windup shaft B by rotation thereof, in other words, since the adjusting belt D is overlapped at the free end and at the tight side thereof and wound up double onto the windup shaft B, a windup radius of the belt D is enlarged with respect to a windup length thereof, and since the windup radius is limited by a collar T attached to the windup shaft B, a windup amount is restricted. Also, the adjusting belt D, which is only inserted into the slit C but not retained thereto, may escape at the free end from the slit C when the belt D is rewound more that the windup amount during the releasing the cargo tightening. Accordingly, a problem is created in that even if the cargoes are upset during the releasing the cargo tightening, such upset cannot be prevented.
When the rewinding is performed more than the windup amount or the anti-reverse-rotation pawl P disengages to release the baggage tightening at a single stroke even if the cargo is not upset, the free end of the adjusting belt D may escape from the slit C. Hence, when the tightening device is reused, it is troublesome that the free end of the adjusting belt D must be again inserted into the slit C.